/**
 * @module tests/unit/brainy/warm
 * @description Coverage for `brain.warm()` / `warmOnOpen` / the provider
 * `warm?()` contract (the cold-restart readiness fix): first operations after
 * a cold restart should run at steady-state cost instead of paying
 * demand-load latency on the critical path.
 *
 * Uses a real, in-process fake plugin provider implementing the actual
 * `VectorIndexProvider` contract from `src/plugin.ts` — the real seam a
 * native provider (e.g. a disk-native accelerator) plugs into. The real
 * built-in JS metadata index and graph adjacency index run against real
 * (filesystem or in-memory) storage with pre-existing data, so their
 * hydration paths are exercised for real, not mocked.
 */
import { describe, it, expect, afterEach } from 'vitest'
import * as fs from 'node:fs'
import * as os from 'node:os'
import * as path from 'node:path'
import { Brainy } from '../../../src/brainy.js'
import { NounType, VerbType } from '../../../src/types/graphTypes.js'
import type { VectorIndexProvider } from '../../../src/plugin.js'
import type { VectorDocument, Vector } from '../../../src/coreTypes.js'
import { MetadataIndexManager } from '../../../src/utils/metadataIndex.js'
import { GraphAdjacencyIndex } from '../../../src/graph/graphAdjacencyIndex.js'

const tmpDirs: string[] = []
function mkTmp(): string {
  const d = fs.mkdtempSync(path.join(os.tmpdir(), 'brainy-warm-'))
  tmpDirs.push(d)
  return d
}
afterEach(() => {
  for (const d of tmpDirs.splice(0)) fs.rmSync(d, { recursive: true, force: true })
})

// Brainy's ValidationConfig fixes vectors at exactly 384 dimensions
// (src/utils/paramValidation.ts) — match it so `add()` doesn't reject test data.
const DIM = 384
const V = (seed = 1): number[] => Array.from({ length: DIM }, (_, i) => Math.sin(seed + i))

/**
 * A real (not mocked) VectorIndexProvider implementation, backed by a plain
 * Map, that optionally implements `warm()` — the exact seam
 * `AddToVectorIndexOperation` / `brain.warm()` call through.
 */
class FakeVectorProvider implements VectorIndexProvider {
  readonly name = 'fake-vector-provider'
  readonly items = new Map<string, Vector>()
  warmCalls = 0
  searchCalls: Array<{ k?: number }> = []
  // Only present on the instance when the constructor is told to — mirrors a
  // real provider that may or may not implement the optional hook. Assigned
  // in the constructor BODY (not as a field initializer): under native ES
  // class fields, field initializers run before constructor-body statements
  // — including the parameter-property assignment — so referencing a
  // parameter property from a field initializer would see it as still
  // `undefined`.
  warm?: () => Promise<void>

  constructor(hasWarm: boolean) {
    if (hasWarm) {
      this.warm = async (): Promise<void> => {
        this.warmCalls++
      }
    }
  }

  async addItem(item: VectorDocument): Promise<string> {
    this.items.set(item.id, item.vector)
    return item.id
  }
  async removeItem(id: string): Promise<boolean> {
    return this.items.delete(id)
  }
  async search(_queryVector: Vector, k?: number): Promise<Array<[string, number]>> {
    this.searchCalls.push({ k })
    return [...this.items.keys()].slice(0, k ?? 10).map((id) => [id, 0])
  }
  size(): number {
    return this.items.size
  }
  clear(): void {
    this.items.clear()
  }
  async rebuild(): Promise<void> {}
  async flush(): Promise<number> {
    return 0
  }
  getPersistMode(): 'immediate' | 'deferred' {
    return 'deferred'
  }
}

/** Registers `provider` under the `'vector'` plugin key, before `init()`. */
function useFakeVectorProvider(brain: Brainy<any>, provider: FakeVectorProvider): void {
  brain.use({
    name: 'fake-vector-provider',
    activate: async (ctx: any) => {
      ctx.registerProvider('vector', () => provider)
      return true
    }
  })
}

describe('brain.warm()', () => {
  it('(a) calls the vector provider\'s warm() when present and reports "warmed"', async () => {
    const brain = new Brainy({
      requireSubtype: false,
      storage: { type: 'memory' },
      silent: true
    })
    const provider = new FakeVectorProvider(true)
    useFakeVectorProvider(brain, provider)
    await brain.init()
    await brain.add({ data: 'a', type: NounType.Thing, vector: V(1) })

    const report = await brain.warm()

    expect(provider.warmCalls).toBe(1)
    expect(provider.searchCalls.length).toBe(0) // warm() ran — no probe fallback
    expect(report.vector.outcome).toBe('warmed')
    await brain.close()
  })

  it('(b) falls back to a probe search() when warm() is absent and reports "probed", never "warmed"', async () => {
    const brain = new Brainy({
      requireSubtype: false,
      storage: { type: 'memory' },
      silent: true
    })
    const provider = new FakeVectorProvider(false)
    useFakeVectorProvider(brain, provider)
    await brain.init()
    await brain.add({ data: 'a', type: NounType.Thing, vector: V(1) })
    await brain.add({ data: 'b', type: NounType.Thing, vector: V(2) })

    const report = await brain.warm()

    expect(provider.warmCalls).toBe(0) // no warm() on this provider
    expect(provider.searchCalls.length).toBe(1) // the probe ran
    expect(provider.searchCalls[0].k).toBe(Math.min(100, provider.size())) // k = min(100, size)
    expect(report.vector.outcome).toBe('probed')
    expect(report.vector.outcome).not.toBe('warmed') // never conflated
    await brain.close()
  })

  it('vector: reports "unavailable" when there is nothing to probe (empty index, unknown dimension)', async () => {
    const brain = new Brainy({
      requireSubtype: false,
      storage: { type: 'memory' },
      silent: true
    })
    // A disk-native provider MAY honestly report 0 resident entries while
    // durable data exists on disk (the same posture documented on
    // `VectorIndexProvider.isReady` — "an mmap/disk-native index may
    // legitimately report 0 resident entries"). warm()'s probe fallback
    // reads `size()`, so this is the real trigger for "nothing to probe":
    // never a k=0 search, an honest skip.
    const provider = new FakeVectorProvider(false)
    provider.size = () => 0
    useFakeVectorProvider(brain, provider)
    await brain.init() // the VFS root bootstrap write sets `dimensions`, but size() still reports 0

    const report = await brain.warm()

    expect(provider.searchCalls.length).toBe(0) // nothing probed
    expect(report.vector.outcome).toBe('unavailable')
    await brain.close()
  })

  it('(c) metadata + graph hydration paths actually execute against filesystem storage with pre-existing data', async () => {
    const dir = mkTmp()

    // Build a brain with real data (including a field NOT in the metadata
    // index's own common-fields warm subset — 'wave' — so hydrateAll()'s
    // FULL hydration is distinguishable from init()'s partial warmCache()),
    // and real graph edges, then close it (persisting everything).
    const seed = new Brainy({
      requireSubtype: false,
      storage: { type: 'filesystem', path: dir },
      silent: true
    })
    await seed.init()
    const ids: string[] = []
    for (let i = 0; i < 6; i++) {
      ids.push(
        await seed.add({
          data: `entity ${i}`,
          type: NounType.Thing,
          metadata: { wave: i % 3 },
          vector: V(i + 1)
        })
      )
    }
    for (let i = 0; i + 1 < ids.length; i++) {
      await seed.relate({ from: ids[i], to: ids[i + 1], type: VerbType.RelatedTo })
    }
    await seed.close()

    // Cold-reopen a FRESH instance and spy on the real hydration seams before
    // calling warm(), so we assert they actually ran (not just that the
    // report claims they did).
    const metaHydrateCalls: number[] = []
    const loadedFields: string[] = []
    const graphInitCalls: number[] = []

    const origHydrateAll = MetadataIndexManager.prototype.hydrateAll
    const origLoadSparseIndex = (MetadataIndexManager.prototype as any).loadSparseIndex
    const origGraphInit = GraphAdjacencyIndex.prototype.init

    MetadataIndexManager.prototype.hydrateAll = async function (...args: any[]) {
      metaHydrateCalls.push(1)
      return origHydrateAll.apply(this, args as any)
    }
    ;(MetadataIndexManager.prototype as any).loadSparseIndex = async function (
      field: string,
      ...args: any[]
    ) {
      loadedFields.push(field)
      return origLoadSparseIndex.apply(this, [field, ...args] as any)
    }
    GraphAdjacencyIndex.prototype.init = async function (...args: any[]) {
      graphInitCalls.push(1)
      return origGraphInit.apply(this, args as any)
    }

    try {
      const brain = new Brainy({
        requireSubtype: false,
        storage: { type: 'filesystem', path: dir },
        silent: true
      })
      await brain.init()

      const report = await brain.warm()

      expect(metaHydrateCalls.length).toBe(1) // hydrateAll() actually ran
      expect(loadedFields).toContain('wave') // a NON-common field was loaded — full hydration, not the heuristic subset
      expect(report.metadata.outcome).toBe('warmed')

      expect(graphInitCalls.length).toBeGreaterThanOrEqual(1) // graph's full-load seam ran (once at brain init, once via warm())
      expect(report.graph.outcome).toBe('warmed')

      // Correctness survives: the hydrated data still answers queries.
      const byWhere = await brain.find({ type: NounType.Thing, where: { wave: 1 } })
      expect(byWhere.length).toBe(2) // waves 1,4 of 0..5

      await brain.close()
    } finally {
      MetadataIndexManager.prototype.hydrateAll = origHydrateAll
      ;(MetadataIndexManager.prototype as any).loadSparseIndex = origLoadSparseIndex
      GraphAdjacencyIndex.prototype.init = origGraphInit
    }
  })

  it('(d) warmOnOpen: true runs warm() during init() — observable via the fake provider', async () => {
    const brain = new Brainy({
      requireSubtype: false,
      storage: { type: 'memory' },
      warmOnOpen: true,
      silent: true
    })
    const provider = new FakeVectorProvider(true)
    useFakeVectorProvider(brain, provider)

    // No explicit brain.warm() call — warmOnOpen must have run it as part of init().
    await brain.init()

    expect(provider.warmCalls).toBe(1)
    await brain.close()
  })

  it('warmOnOpen defaults to false — init() does NOT run warm() unless opted in', async () => {
    const brain = new Brainy({
      requireSubtype: false,
      storage: { type: 'memory' },
      silent: true
    })
    const provider = new FakeVectorProvider(true)
    useFakeVectorProvider(brain, provider)

    await brain.init()

    expect(provider.warmCalls).toBe(0)
    await brain.close()
  })

  it('(e) WarmReport shape: outcome literal + durationMs per surface, plus totalDurationMs', async () => {
    const brain = new Brainy({
      requireSubtype: false,
      storage: { type: 'memory' },
      silent: true
    })
    const provider = new FakeVectorProvider(true)
    useFakeVectorProvider(brain, provider)
    await brain.init()
    await brain.add({ data: 'a', type: NounType.Thing, vector: V(1) })

    const report = await brain.warm()

    for (const surface of ['vector', 'metadata', 'graph'] as const) {
      expect(['warmed', 'probed', 'unavailable']).toContain(report[surface].outcome)
      expect(typeof report[surface].durationMs).toBe('number')
      expect(report[surface].durationMs).toBeGreaterThanOrEqual(0)
    }
    expect(typeof report.totalDurationMs).toBe('number')
    expect(report.totalDurationMs).toBeGreaterThanOrEqual(0)
    await brain.close()
  })

  // --- Metadata leg routes through the ACTIVE provider (8.10.1) -----------
  //
  // `MetadataIndexProvider` is a ~50-method interface (src/plugin.ts) — far
  // too large to hand-write a compliant fake class the way `FakeVectorProvider`
  // fakes the ~8-method `VectorIndexProvider` above. Test (c) already
  // establishes this file's pattern for the metadata leg: exercise the REAL
  // `MetadataIndexManager` instance and shape just the probe points brain.ts
  // reads (`typeof provider.warm === 'function'` /
  // `typeof provider.hydrateAll === 'function'`) directly on that instance.
  // Shadowing an own property on the live object stands in for "a different
  // provider implementation" without needing a hand-rolled full fake — the
  // rest of the real manager (used by add()/init() above) is untouched.
  describe('metadata leg — warm() routes through the active provider', () => {
    it('(f) calls the ACTIVE metadata provider\'s warm() when present and reports "warmed", never falling back to hydrateAll', async () => {
      const brain = new Brainy({
        requireSubtype: false,
        storage: { type: 'memory' },
        silent: true
      })
      await brain.init()
      await brain.add({ data: 'a', type: NounType.Thing, vector: V(1) })

      const metadataIndex = (brain as any).metadataIndex
      let warmCalls = 0
      let hydrateAllCalls = 0
      const origHydrateAll = metadataIndex.hydrateAll.bind(metadataIndex)
      metadataIndex.hydrateAll = async (...args: unknown[]) => {
        hydrateAllCalls++
        return origHydrateAll(...args)
      }
      // Simulates a native metadata provider declaring the optional `warm()`
      // hook added to `MetadataIndexProvider` (src/plugin.ts) in 8.10.1.
      metadataIndex.warm = async () => {
        warmCalls++
      }

      const report = await brain.warm()

      expect(warmCalls).toBe(1)
      expect(hydrateAllCalls).toBe(0) // warm() ran — no hydrateAll fallback
      expect(report.metadata.outcome).toBe('warmed')
      await brain.close()
    })

    it('reports "unavailable" when the active metadata provider implements neither warm() nor hydrateAll() (the honest branch a native provider without either hook must hit)', async () => {
      const brain = new Brainy({
        requireSubtype: false,
        storage: { type: 'memory' },
        silent: true
      })
      await brain.init()
      await brain.add({ data: 'a', type: NounType.Thing, vector: V(1) })

      const metadataIndex = (brain as any).metadataIndex
      // Shadow away BOTH optional hooks — models a genuinely native provider
      // that (unlike the built-in JS manager) offers neither seam. This must
      // never fall back to calling init() as a stand-in for warmth.
      metadataIndex.warm = undefined
      metadataIndex.hydrateAll = undefined

      const report = await brain.warm()

      expect(report.metadata.outcome).toBe('unavailable')
      await brain.close()
    })

    it('the built-in JS manager (no warm()) still reports "warmed" via its existing hydrateAll() duck-type — unchanged by the new provider hook', async () => {
      const brain = new Brainy({
        requireSubtype: false,
        storage: { type: 'memory' },
        silent: true
      })
      await brain.init()
      await brain.add({ data: 'a', type: NounType.Thing, vector: V(1) })

      // No patching at all — the default built-in MetadataIndexManager has
      // hydrateAll() but no warm(), exactly as it did before this change.
      const metadataIndex = (brain as any).metadataIndex
      expect(typeof metadataIndex.warm).not.toBe('function')
      expect(typeof metadataIndex.hydrateAll).toBe('function')

      const report = await brain.warm()

      expect(report.metadata.outcome).toBe('warmed')
      await brain.close()
    })
  })
})